Fig. 4

Shape descriptors of dark vs typical microglia. Representative 5 nm resolution scanning electron microscopy images captured in the ventral hippocampus CA1 stratum lacunosum-moleculare of 20-month-old APP-PS1 and C57BL/6J male mice. A typical microglia (TM) in C57BL/6J mice, B TM far from Aβ plaque, (C) TM near Aβ plaques and dystrophic neurites, (D) dark microglia (DM) near Aβ plaques and dystrophic neurites in APP-PS1 mice. E–I Graphs representing the shape descriptors of microglia: (E) area, (F) perimeter, (G) circularity, (H) aspect ratio and (I) solidity. Data shown are expressed as means ± S.E.M. *p < 0.05, **p < 0.01, using a Kruskal–Wallis test with a Dunn’s multiple comparisons post hoc test. Statistical tests were performed on n = 9–12 microglia per animal with N = 3 mice/group, for a total of 111 microglial cell bodies analyzed. Red outline = plasma membrane, yellow outline = nuclear membrane. A = axon terminals, S = dendritic spines, orange asterisk = mitochondria, green asterisk = altered mitochondria, blue asterisk = endoplasmic reticulum, red arrow = Golgi apparatus, lb = lipid body, 3rd = tertiary lysosome, 2nd = secondary lysosome, Lg = lipofuscin granules, pink pseudo-coloring = dystrophic neurites